Mass mortalities limit the viability of mammal populations; particularly those of endangered species with reduced population sizes. Die-offs of the Critically Endangered saiga antelope (Saiga tatarica) were reported in 2010 and 2011, post-calving.

The current but untested hypothesis is that a combination of
unusual weather, topography and pasture improvement resulted in
fast-growing, moist and atypically composed forage, which caused a
form of metabolite toxicosis.

An analysis of assumptions underlying this hypothesis using
meteorological data and satellite imagery revealed that neither
temporal variation in weather nor highly-productive, moist forage
are likely to have been factors in the die-offs; although
significantly lower vegetation or soil moisture in die-off zones
than in the surrounding landscape indicates events were
location-dependent, and therefore precipitated by changes in
calving site selection driven by human environmental
perturbations.

Unusual topography and pasture improvement in these locations
probably promoted legume-rich pastures which triggered a condition
more closely related to bloat, although variables may be acting at
scales finer than assessed, signifying a need for local assessment
of die-off pastures and demarcation of similar areas. High natural
mortality during saiga calving with various aetiologies indicates
an urgent need to limit disturbance at this vulnerable time and
increase population sizes to prevent local extirpation.